Methacrylic resin composition for non-contact hot plate welding, molded article, and method for producing same

ABSTRACT

The present invention provides a methacrylic resin composition for non-contact hot plate welding comprising a methacrylic resin comprising 80 to 99.9% by mass of a methacrylic acid ester monomer unit and 0.1 to 20% by mass of a unit of at least one additional vinyl monomer copolymerizable with the methacrylic acid ester monomer, wherein the methacrylic resin composition has a melt flow rate (MFR) of 2.5 g/10 min or lower at 230° C. at a load of 3.8 kg.

TECHNICAL FIELD

The present invention relates to a methacrylic resin composition fornon-contact hot plate welding, a molded article, and a method forproducing the same.

BACKGROUND ART

Methacrylic resin compositions are excellent in transparency and weatherresistance and as such, have heretofore been used as raw materials for,for example, members for vehicles such as taillight covers, headlightcovers, and meter panels (see e.g., Patent Literatures 1 and 2).

The members for vehicles are prepared by joining a housing member madeof, for example, a styrene-based resin such as an ABS resin to a membermade of a methacrylic resin composition, followed by processing.

For example, a method using an adhesive, a hot plate welding method, anda vibration welding method are known as methods for joining astyrene-based resin or the like to a member made of a methacrylic resincomposition (see e.g., Patent Literature 3).

The hot plate welding method is a method which involves each heating therespective parts to be joined of the members mentioned above in closecontact with a hot plate made of a metal so that the parts are melted,followed by the pressure bonding of these parts. This method can omitthe step of applying an adhesive and the curing time of the adhesive andis therefore excellent in productivity.

On the other hand, the hot plate welding method may cause the phenomenonin which, after the melting with a hot plate made of a metal heated to apredetermined temperature, a portion of the resin composition, whenseparated from the hot plate, are stretched in a string-like shapewithout being well detached from the hot plate (so-called stringiness).Such a resin composition may become responsible for poor appearance whenused as a raw material for a member for vehicles (see e.g., PatentLiterature 4).

CITATION LIST Patent Literature

-   Patent Literature 1: Japanese Patent Laid-Open No. 08-302145-   Patent Literature 2: Japanese Patent Laid-Open No. 05-247311-   Patent Literature 3: Japanese Patent Laid-Open No. 2005-239823-   Patent Literature 4: Japanese Patent Laid-Open No. 2009-249529

SUMMARY OF INVENTION Technical Problem

A method which involves heating the resin composition without beingbrought into direct contact with the hot plate made of a metal, i.e., inno contact with the hot plate, so that the surface of the resincomposition is melted, followed by pressure bonding (non-contact hotplate welding method) is effective for solving the problem of so-calledstringiness as mentioned above.

This non-contact hot plate welding method has the advantage that poorappearance such as stringiness is less likely to occur as compared withthe hot plate welding method, because the resin is melted by radiationheat from the hot plate.

For the non-contact hot plate welding method, as with the hot platewelding method mentioned above, it is desirable that the respectiveparts to be joined of the members should be melted in a short time, fromthe viewpoint of productivity. Therefore, a high hot plate temperatureis preferred. In addition, since the resin is melted by radiation heatfrom the hot plate, the hot plate temperature needs to be on the orderof at least 500° C.

Some conventional methacrylic resin compositions, however, may be foundto generate bubbles during melting with the hot plate thus heated. Sucha resin composition disadvantageously becomes responsible for poorappearance when used as a raw material for the member for vehicles.

Accordingly, an object of the present invention is to provide amethacrylic resin composition for non-contact hot plate welding which iscapable of effectively suppressing bubble generation when used in thenon-contact hot plate welding method, a molded article comprising themethacrylic resin composition, and a method for producing the same.

Solution to Problem

The present inventors have conducted diligent studies in light of theproblems of the conventional techniques mentioned above and consequentlycompleted the present invention by finding that a methacrylic resincomposition comprising a methacrylic resin comprising predeterminedamounts of a methacrylic acid ester monomer unit and a unit of at leastone additional vinyl monomer copolymerizable with the methacrylic acidester monomer, and having a melt flow rate (MFR) equal to or lower thana particular numeric value at 230° C. at a load of 3.8 kg is less likelyto generate bubbles when used in the non-contact hot plate weldingmethod.

Specifically, the present invention is as follows.

-   [1]

A methacrylic resin composition for non-contact hot plate weldingcomprising a methacrylic resin comprising 80 to 99.9% by mass of amethacrylic acid ester monomer unit and 0.1 to 20% by mass of a unit ofat least one additional vinyl monomer copolymerizable with themethacrylic acid ester monomer, wherein the methacrylic resincomposition has a melt flow rate (MFR) of 2.5 g/10 min or lower at 230°C. at a load of 3.8 kg.

-   [2]

The methacrylic resin composition for non-contact hot plate weldingaccording to the [1], wherein the methacrylic resin is a methacrylicresin which

has a weight-average molecular weight of 300000 or lower as measured bygel permeation chromatography (GPC), and contains 6 to 50% of acomponent having a molecular weight that is 5 times or more lower than apeak top molecular weight (Mp) obtained from a GPC elution curve.

-   [3]

The methacrylic resin composition for non-contact hot plate weldingaccording to the [1] or [2], wherein the methacrylic resin is amethacrylic resin in which

an abundance of a component having a molecular weight of 250000 orhigher obtained from the GPC elution curve is 12% or more of a GPC area.

-   [4]

The methacrylic resin composition for non-contact hot plate weldingaccording to any one of the [1] to [3], wherein the methacrylic resin

has an extrapolated onset temperature (° C.) of 120° C. or lower asdetermined from a glass transition curve obtained by heating from 40° C.to 210° C. at a heating rate of 10° C./min according to JIS-K-7121 withα-alumina as a reference in a nitrogen gas atmosphere using adifferential scanning calorimeter (DSC).

-   [5]

The methacrylic resin composition for non-contact hot plate weldingaccording to any one of the [1] to [4], wherein the methacrylic resincomposition is used as a raw material for a member for a vehicle.

-   [6]

The methacrylic resin composition for non-contact hot plate weldingaccording to the [5], wherein the member for the vehicle is at least onemember selected from the group consisting of a taillight cover, aheadlight cover, and a meter panel.

-   [7]

A molded article comprising a molded article (A) welded with anadditional molded article (B),

the molded article (A) comprising a methacrylic resin comprising 80 to99.9% by mass of a methacrylic acid ester monomer unit and 0.1 to 20% bymass of a unit of at least one additional vinyl monomer copolymerizablewith the methacrylic acid ester monomer, wherein

the molded article (A) has a melt flow rate (MFR) of 2.5 g/10 min orlower at 230° C. at a load of 3.8 kg.

-   [8]

The molded article according to the [7], wherein the methacrylic resinis a methacrylic resin which

has a weight-average molecular weight of 300000 or lower as measured bygel permeation chromatography (GPC), and

contains 6 to 50% of a component having a molecular weight that is 5times or more lower than a peak top molecular weight (Mp) obtained froma GPC elution curve.

-   [9]

The molded article according to the [7] or [8], wherein the methacrylicresin is a methacrylic resin in which

an abundance of a component having a molecular weight of 250000 orhigher obtained from the GPC elution curve is 12% or more of a GPC area.

-   [10]

The molded article according to any one of the [7] to [9], wherein themethacrylic resin

has an extrapolated onset temperature (° C.) of 120° C. or lower asdetermined from a glass transition curve obtained by heating from 40° C.to 210° C. at a heating rate of 10° C./min according to JIS-K-7121 withα-alumina as a reference in a nitrogen gas atmosphere using adifferential scanning calorimeter (DSC).

-   [11]

The molded article according to any one of the [7] to [10], wherein themolded article (A) has a water absorption rate of 0.5% by mass or lower.

-   [12]

The molded article according to any one of the [7] to [11], wherein themolded article is used as a raw material for a member for a vehicle.

-   [13]

The molded article according to the [12], wherein the member for thevehicle is at least one member selected from the group consisting of ataillight cover, a headlight cover, and a meter panel.

-   [14]

The molded article according to any one of the [7] to [13], wherein themolded article (B) is a molded article of an ABS-based resin.

-   [15]

A member for a vehicle, comprising the molded article according to anyone of the [7] to [14].

-   [16]

The member for the vehicle according to the [15], wherein the member forthe vehicle is at least one member selected from the group consisting ofa taillight cover, a headlight cover, and a meter panel.

-   [17]

A method for producing a molded article, comprising the steps of:

heating a molded article (A) in no contact with a hot plate so that asurface of the molded article (A) is melted, the molded article (A)comprising a methacrylic resin comprising 80 to 99.9% by mass of amethacrylic acid ester monomer unit and 0.1 to 20% by mass of a unit ofat least one additional vinyl monomer copolymerizable with themethacrylic acid ester monomer, wherein the molded article (A) has amelt flow rate (MFR) of 2.5 g/10 min or lower at 230° C. at a load of3.8 kg; and

welding the molded article (A) with an additional molded article (B).

-   [18]

The method for producing the molded article according to the [17],wherein the methacrylic resin is a methacrylic resin which has aweight-average molecular weight of 300000 or lower as measured by gelpermeation chromatography (GPC), and which contains 6 to 50% of acomponent having a molecular weight that is 5 times or more lower than apeak top molecular weight (Mp) obtained from a GPC elution curve.

-   [19]

The method for producing the molded article according to the [17] or[18], wherein the methacrylic resin is a methacrylic resin in which

an abundance of a component having a molecular weight of 250000 orhigher obtained from the GPC elution curve is 12% or more of a GPC area.

-   [20]

The method for producing the molded article according to any one of the[17] to [19], wherein the methacrylic resin

has an extrapolated onset temperature (° C.) of 120° C. or lower asdetermined from a glass transition curve obtained by heating from 40° C.to 210° C. at a heating rate of 10° C./min according to JIS-K-7121 withα-alumina as a reference in a nitrogen gas atmosphere using adifferential scanning calorimeter (DSC).

-   [21]

The method for producing the molded article according to any one of the[17] to [20], wherein the molded article (A) has a water absorption rateof 0.5% by mass or lower.

-   [22]

The method for producing the molded article according to any one of the[17] to [21], wherein the molded article (B) is a molded article of anABS-based resin.

Advantageous Effects of Invention

The present invention can provide a methacrylic resin composition fornon-contact hot plate welding which can effectively reduce bubblegeneration when used in the non-contact hot plate welding method, whichproduces a molded article having the favorable appearance of weldedsurface, and which is also excellent in flowability in molding.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic cross-sectional view of a molded article forillustrating the non-contact hot plate welding method.

DESCRIPTION OF EMBODIMENTS

Hereinafter, the mode for carrying out the present invention(hereinafter, referred to as the “present embodiment”) will be describedin detail. The present embodiment described below is merely given forillustrating the present invention and is not intended to limit thepresent invention to the contents described below. The present inventioncan be carried out by making appropriate change or modification withoutdeparting from the spirit of the present invention.

In the present specification, each monomer component beforepolymerization is referred to as an “XX monomer”, and the term “monomer”may be omitted.

Also, each constitutional unit constituting a polymer is referred to asan “XX monomer unit” and may be simply referred to as an “XX unit”.

[Methacrylic Resin Composition for Non-Contact Hot Plate Welding]

The methacrylic resin composition for non-contact hot plate welding(hereinafter, also simply referred to as the “methacrylic resincomposition”) of the present embodiment comprises

a methacrylic resin comprising 80 to 99.9% by mass of a methacrylic acidester monomer unit and 0.1 to 20% by mass of a unit of at least oneadditional vinyl monomer copolymerizable with the methacrylic acid estermonomer, wherein

the methacrylic resin composition has a melt flow rate (MFR) of 2.5 g/10min or lower at 230° C. at a load of 3.8 kg.

(Methacrylic Resin)

The methacrylic resin contained in the methacrylic resin composition ofthe present embodiment comprises 80 to 99.9% by mass of a methacrylicacid ester monomer unit and 0.1 to 20% by mass of a unit of at least oneadditional vinyl monomer copolymerizable with the methacrylic acid estermonomer.

<Methacrylic Acid Ester Monomer>

The methacrylic acid ester monomer constituting the methacrylic resin isnot particularly limited as long as the effects of the present inventioncan be achieved. Preferred examples thereof include a monomerrepresented by the following general formula (1):

In the general formula (1), R₁ represents a methyl group.

R₂ represents a hydrocarbon group having 1 to 18 carbon atoms in which ahydrogen atom on carbon may be replaced with a hydroxy group or ahalogen group.

Examples of the methacrylic acid ester monomer include, but are notlimited to, butyl methacrylate, ethyl methacrylate, methyl methacrylate,propyl methacrylate, isopropyl methacrylate, isobutyl methacrylate,cyclohexyl methacrylate, phenyl methacrylate, (2-ethylhexyl)methacrylate, (t-butylcyclohexyl) methacrylate, benzyl methacrylate, and(2,2,2-trifluoroethyl) methacrylate. Methyl methacrylate, ethylmethacrylate, or propyl methacrylate is more preferred, and methylmethacrylate is further preferred, from the viewpoint of handling andeasy availability.

Only one of these methacrylic acid ester monomers may be used alone, ortwo or more thereof may be used in combination.

<Additional Vinyl Monomer Copolymerizable with Methacrylic Acid EsterMonomer>

The additional vinyl monomer copolymerizable with the methacrylic acidester monomer mentioned above, constituting the methacrylic resincontained in the methacrylic resin composition of the present embodimentis not particularly limited as long as the effects of the presentinvention can be achieved. Preferred examples thereof include an acrylicacid ester monomer represented by the following general formula (2):

In the general formula (2), R₃ represents a hydrogen atom, and R₄represents a hydrocarbon group having 1 to 18 carbon atoms in which ahydrogen atom on carbon may be replaced with a hydroxy group or ahalogen group.

Examples of the acrylic acid ester monomer represented by the generalformula (2) include, but are not limited to, methyl acrylate, ethylacrylate, propyl acrylate, butyl acrylate, isobutyl acrylate, cyclohexylacrylate, phenyl acrylate, (2-ethylhexyl) acrylate, (t-butylcyclohexyl)acrylate, benzyl acrylate, and (2,2,2-trifluoroethyl) acrylate.

Methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate,butyl acrylate, isobutyl acrylate, or the like is more preferred, andmethyl acrylate is further preferred, from the viewpoint of handling andeasy availability.

Examples of the additional vinyl monomer other than the acrylic acidester monomer of the general formula (2), copolymerizable with themethacrylic acid ester monomer include, but are not limited to:α,β-unsaturated acids such as acrylic acid and methacrylic acid;unsaturated group-containing divalent carboxylic acids such as maleicacid, fumaric acid, itaconic acid, and cinnamic acid, and their alkylesters; styrene-based monomers such as styrene, o-methylstyrene,m-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene,2,5-dimethylstyrene, 3,4-dimethylstyrene, 3,5-dimethylstyrene,p-ethylstyrene, m-ethylstyrene, o-ethylstyrene, p-tert-butylstyrene, andisopropenylbenzene(α-methylstyrene); aromatic vinyl compounds such as1-vinylnaphthalene, 2-vinylnaphthalene, 1,1-diphenylethylene,isopropenyltoluene, isopropenylethylbenzene, isopropenylpropylbenzene,isopropenylbutylbenzene, isopropenylpentylbenzene,isopropenylhexylbenzene, and isopropenyloctylbenzene; vinyl cyanidecompounds such as acrylonitrile and methacrylonitrile; unsaturatedcarboxylic anhydrides such as maleic anhydride and itaconic anhydride;maleimide and N-substituted maleimides such as N-methylmaleimide,N-ethylmaleimide, N-phenylmaleimide, and N-cyclohexylmaleimide; amidessuch as acrylamide and methacrylamide; ethylene glycol or oligomersthereof whose both terminal hydroxy groups have been esterified withacrylic acid or methacrylic acid, such as ethylene glycol di(meth)acrylate, diethylene glycol di (meth)acrylate, triethylene glycoldi (meth)acrylate, and tetraethylene glycol di (meth)acrylate; alcoholswhose two hydroxy groups have been esterified with acrylic acid ormethacrylic acid, such as neopentyl glycol di (meth)acrylate and di(meth)acrylate; polyhydric alcohol derivatives, such astrimethylolpropane, pentaerythritol, esterified with acrylic acid ormethacrylic acid; and polyfunctional monomers such as divinylbenzene.

Only one of these acrylic acid ester monomers represented by the generalformula (2) copolymerizable with the methacrylic acid ester monomer orvinyl-based monomers other than the above-listed acrylic acid estermonomers represented by the general formula (2) may be used alone, ortwo or more thereof may be used in combination.

The content of the unit of the additional vinyl monomer copolymerizablewith the methacrylic acid ester monomer mentioned above, constitutingthe methacrylic resin is 0.1 to 20% by mass in the methacrylic resin.

When the content of the unit of the additional vinyl monomercopolymerizable with the methacrylic acid ester monomer mentioned aboveis 0.1% by mass orhigher, flowability and heat resistance can beimproved. When this content is 20% by mass or lower, heat resistance canbe enhanced.

The content is preferably 0.1 to 17% by mass, more preferably 0.2 to 15%by mass, further preferably 0.3 to 12% by mass.

For the methacrylic resin, a vinyl-based monomer other than theabove-listed vinyl monomers, copolymerizable with the methacrylic acidester monomer may be appropriately added and copolymerized therewith,for the purpose of improving properties such as heat resistance andprocessability.

The total amount of the methacrylic acid ester monomer unit and the unitof the vinyl monomer copolymerizable with the methacrylic acid ester isset to 100% by mass.

(Properties of Methacrylic Resin) <Weight-Average Molecular Weight andMolecular Weight Distribution of Methacrylic Resin>

The weight-average molecular weight and the molecular weightdistribution of the methacrylic resin contained in the methacrylic resincomposition of the present embodiment will be described.

The methacrylic resin preferably has a weight-average molecular weight(Mw) of 300000 or lower as measured by GPC (gel permeationchromatography).

For obtaining excellent mechanical strength and solvent resistance, theweight-average molecular weight (Mw) of the methacrylic resin ispreferably 50000 orhigher, more preferably 60000 or higher, furtherpreferably 70000 or higher, still further preferably 80000 or higher,still further preferably 90000 or higher.

For exerting the favorable flowability of the methacrylic resin, theweight-average molecular weight (Mw) is preferably 300000 orlower, morepreferably 250000 or lower, further preferably 230000 or lower, stillfurther preferably 210000 or lower, still further preferably 180000 orlower.

When the weight-average molecular weight of the methacrylic resin fallswithin the range mentioned above, flowability, mechanical strength, andsolvent resistance can be well balanced and favorable moldingprocessability is maintained.

The molecular weight distribution (Mw/Mn) of the methacrylic resincontained in the methacrylic resin composition of the present embodimentis preferably 1.6 to 6.0, more preferably 1.7 to 5.0, further preferably1.8 to 5.0. When the molecular weight distribution of the methacrylicresin is 1.6 or more and 6.0 or less, the effect of attaining theexcellent balance between flowability in the molding process andmechanical strength is obtained.

The weight-average molecular weight (Mw) and the number-averagemolecular weight (Mn) of the methacrylic resin can be measured by gelpermeation chromatography (GPC) and can be specifically measured by amethod described in [Examples] mentioned later.

Specifically, a calibration curve is prepared in advance from elutiontimes and weight-average molecular weights using monodisperse standardmethacrylic resins that have a known weight-average molecular weight andare available as reagents, and an analytical gel column that eluteshigh-molecular-weight components first. Subsequently, the weight-averagemolecular weight (Mw) and the number-average molecular weight (Mn) of apredetermined analyte methacrylic resin can be determined on the basisof the obtained calibration curve. The molecular weight distribution canbe calculated from these values.

The number-average molecular weight (Mn) is an average molecular weightper one simple molecule and is defined by the total weight of thesystem/the number of the molecule in the system.

The weight-average molecular weight (Mw) is defined by an averagemolecular weight based on weight fraction.

<Abundance of Component Having Molecular Weight that is 5 Times or MoreLower Than Peak Top Molecular Weight (Mp)>

In the methacrylic resin, the abundance of a component having amolecular weight that is 5 times or more lower than a peak top molecularweight (Mp) is preferably 6 to 50%, more preferably 8 to 45%, furtherpreferably 10 to 43%, still further preferably 12 to 40%, still furtherpreferably 15 to 38%, from the viewpoint of solvent resistance,flowability in the molding process, and the suppression of bubblegeneration during non-contact hot plate welding.

In this context, the abundance (%) of the component having a molecularweight that is 5 times or more lower than a peak top molecular weight(Mp) is the ratio of an area corresponding to the component having amolecular weight that is 5 times or more lower than a peak top molecularweight (Mp) to the total area of the GPC elution curve defined as 100%,and can be measured by a method described in [Examples] mentioned later.

The peak top molecular weight (Mp) refers to a weight molecular weightthat shows a peak in the GPC elution curve.

When a plurality of peaks are present in the GPC elution curve, amolecular weight at a peak shown by a weight molecular weight with thelargest abundance is used as the peak top molecular weight (Mp).

When the abundance of the component having a molecular weight that is 5times or more lower than a peak top molecular weight (Mp) in themethacrylic resin is 6% or higher, favorable flowability in molding isobtained. When this abundance is 50% orlower, favorable solventresistance and bubble generation-suppressing effect are obtained.

A minimum amount of a methacrylic resin component having aweight-average molecular weight of 500 or lower is preferred because thegeneration of foam-like poor appearance called silver is preventedduring molding.

<Abundance of Component Having Molecular Weight of 250000 or HigherObtained from GPC Elution Curve>

In the methacrylic resin contained in the methacrylic resin compositionof the present embodiment, the abundance of a component having amolecular weight of 250000 or higher with respect to the total area ofthe GPC elution curve defined as 100% is preferably 12% or more of theGPC area from the viewpoint of solvent resistance and the suppression ofbubble generation during non-contact hot plate welding. This abundanceis more preferably 13% or more, further preferably 14% or more.

The abundance of the component having a molecular weight of 250000 orhigher in the methacrylic resin can be measured by a method described in[Examples] mentioned later.

<Extrapolated Onset Temperature Measured Using Differential ScanningCalorimeter>

The methacrylic resin contained in the methacrylic resin composition ofthe present embodiment preferably has an extrapolated onset temperature(° C.) of 120° C. or lower as determined from a glass transition curveobtained by heating from 40° C. to 210° C. at a heating rate of 10°C./min according to JIS-K-7121 with α-alumina as a reference in anitrogen gas atmosphere using a differential scanning calorimeter (DSC).

A lower value of the extrapolated onset temperature (° C.) obtained by ameasurement method described in [Examples] mentioned later means thateasy melting as a resin is more improved. This value influencesreduction in uneven melting in no contact with a hot plate or theappearance of welded surface. Thus, the extrapolated onset temperatureof the methacrylic resin contained in the methacrylic resin compositionof the present embodiment is preferably 120° C. or lower, morepreferably 115° C. or lower, further preferably 113° C. or lower.

(Method for ProducingMmethacrylic resin)

The methacrylic resin contained in the methacrylic resin composition ofthe present embodiment can be produced by any polymerization method ofbulk polymerization, solution polymerization, suspension polymerization,and emulsion polymerization methods. The polymerization method ispreferably a bulk polymerization, solution polymerization, or suspensionpolymerization method, more preferably a suspension polymerizationmethod.

The polymerization temperature can be appropriately selected as anoptimum polymerization temperature according to the polymerizationmethod and is preferably 50° C. or higher and 100° C. or lower, morepreferably 60° C. or higher and 90° C. or lower.

A polymerization initiator may be used in the production of themethacrylic resin.

Examples of the polymerization initiator include, but are not limitedto: organic peroxides such as di-t-butyl peroxide, lauroyl peroxide,stearyl peroxide, benzoyl peroxide, t-butyl peroxyneodecanoate, t-butylperoxypivalate, dilauroyl peroxide, dicumyl peroxide, t-butylperoxy-2-ethylhexanoate,1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, and1,1-bis(t-butylperoxy)cyclohexane; and general azo-based radicalpolymerization initiators such as azobisisobutyronitrile,azobisisovaleronitrile, 1,1-azobis(1-cyclohexanecarbonitrile),2,2′-azobis-4-methoxy-2,4-azobisisobutyronitrile,2,2′-azobis-2,4-dimethylvaleronitrile, and2,2′-azobis-2-methylbutyronitrile, for radical polymerization.

Only one of these polymerization initiators may be used alone, or two ormore types thereof may be used in combination.

Any of these radical initiators may be combined with an appropriatereducing agent and used as a redox-based initiator.

The radical polymerization initiator and/or the redox-based initiator isgenerally used in the range of 0 to 1 part by mass with respect to 100parts by mass in total of all monomers for use in the polymerization forthe methacrylic resin. The amount of the radical polymerizationinitiator and/or the redox-based initiator used can be appropriatelyselected in consideration of the temperature at which the polymerizationis performed, and the half-life of the polymerization initiator.

In the case of selecting a bulk polymerization method, a castpolymerization method, or a suspension polymerization method as thepolymerization method for the methacrylic resin, the polymerization ispreferably performed using a peroxide-based polymerization initiator,from the viewpoint of preventing the staining of the methacrylic resin.

Examples of the peroxide-based polymerization initiator include, but arenot limited to, lauroyl peroxide, decanoyl peroxide, and t-butylperoxy-2-ethylhexanoate. Lauroyl peroxide is more preferred.

For performing the polymerization for the methacrylic resin by thesolution polymerization method at a high temperature of 90° C. orhigher, it is preferred to use, for example, a peroxide or azobisinitiator that has a 10-hour half-life temperature of 80° C. or higherand is soluble in an organic solvent used, as the polymerizationinitiator.

Examples of the peroxide or azobis initiator include, but are notlimited to, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane,cyclohexane peroxide, 2,5-dimethyl-2,5-di (benzoylperoxy)hexane,1,1-azobis(1-cyclohexanecarbonitrile), and 2-(carbamoylazo)isobutyronitrile.

For the production of the methacrylic resin, the molecular weight of themethacrylic resin may be controlled without impairing the object of thepresent invention.

Examples of the method for controlling the molecular weight of themethacrylic resin include, but are not limited to, a method ofcontrolling the molecular weight by using, for example, a chain transferagent such as alkylmercaptans, dimethylacetamide, dimethylformamide, ortriethylamine, and an iniferter such as dithiocarbamates,triphenylmethylazobenzene, or a tetraphenylethane derivative.Alternatively, the molecular weight may be adjusted by adjusting theamounts of these agents added.

The chain transfer agent is preferably alkylmercaptans from theviewpoint of handleability and stability. Examples of thealkylmercaptans include, but are not limited to, n-butylmercaptan,n-octylmercaptan, n-dodecylmercaptan, t-dodecylmercaptan,n-tetradecylmercaptan, n-octadecylmercaptan, 2-ethylhexyl thioglycolate,ethylene glycol dithioglycolate, trimethylolpropane tris(thioglycolate),and pentaerythritol tetrakis(thioglycolate).

These agents can be appropriately added according to the intendedmolecular weight of the methacrylic resin and are generally used in therange of 0.001 parts by mass to 3 parts by mass with respect to 100parts by mass in total of all monomers for use in the polymerization forthe methacrylic resin.

Other examples of the method for controlling the molecular weightinclude a method of changing the polymerization method, a method ofadjusting the amount of the polymerization initiator, the chain transferagent or the iniferter mentioned above, etc., and a method of changingvarious polymerization conditions such as polymerization temperature.

In the methacrylic resin contained in the methacrylic resin compositionof the present embodiment, the abundance of a component having amolecular weight of 250000 or higher obtained from the GPC elution curvecan also be controlled by the application of these methods forcontrolling the molecular weight.

Only one of these methods for controlling the molecular weight may beused, or two or more of these methods may be used in combination.

Examples of the method for producing the methacrylic resin in which theabundance of a component having a molecular weight that is 5 times ormore lower than a peak top molecular weight (Mp) obtained from a GPCelution curve is in the range of 6 to 50% include a method ofmelt-blending a low-molecular-weight methacrylic resin and ahigh-molecular-weight methacrylic resin, and a production method basedon a multistage polymerization method.

The method is not particularly limited as long as the abundance of 6 to50% can be achieved for the component having a molecular weight that is5 times or more lower than the Mp. A multistage polymerization method ismore preferably used from the viewpoint of quality stability.

In the case of using the multistage polymerization method, it ispreferred to first use a raw material mixture constituted by amethacrylic acid ester monomer and at least one additional vinyl monomercopolymerizable with the methacrylic acid ester monomer in thefirst-stage polymerization to produce 5 to 50% by mass of a polymer (I)having a weight-average molecular weight of 5000 to 50000 as measured byGPC with respect to the whole of the methacrylic resin of interest.

Next, the inside of the polymerization system is kept at a temperaturehigher than the first-stage polymerization temperature for a given time.

It is preferred to then add a raw material mixture constituted by amethacrylic acid ester monomer and at least one additional vinyl monomercopolymerizable with the methacrylic acid ester monomer in the presenceof the polymer (I) and polymerize them to produce 95 to 50% by mass of apolymer (II) having a weight-average molecular weight of 60000 to 350000with respect to the whole of the methacrylic resin of interest.

The mixing ratio between the polymer (I) having a weight-averagemolecular weight of 5000 to 50000 as measured by GPC (hereinafter,simply referred to as the polymer (I)) obtained in the first-stagepolymerization, and the polymer (II) having a weight-average molecularweight of 60000 to 350000 (hereinafter, simply referred to as thepolymer (II)) obtained in the second-stage polymerization by adding araw material mixture containing a methacrylic acid ester in the presenceof the polymer (I) is preferably 5 to 50% by mass of the polymer (I) and95 to 50% by mass of the polymer (II) from the viewpoint ofpolymerization stability during production and improvement in theflowability of the methacrylic resin and the mechanical strength of aresin molded article.

The polymer (I)/polymer (II) ratio is more preferably 7 to 47% bymass/93 to 53% by mass, further preferably 10 to 45% by mass/90 to 55%by mass, still further preferably 13 to 43% by mass/87 to 57% by mass,still further preferably 15 to 40% by mass/85 to 60% by mass, inconsideration of the balance among polymerization stability,flowability, and the mechanical strength of a molded article.

The polymer (I) is preferably a polymer comprising 80 to 100% by mass ofa methacrylic acid ester monomer unit and 0 to 20% by mass of a monomerunit constituted by at least one additional vinyl monomercopolymerizable with the methacrylic acid ester.

The ratios of the monomer units constituting the polymer (I) can beadjusted by controlling the amounts of the monomers added in thepolymerization step for the polymer (I) in the multistagepolymerization.

In the polymer (I), a smaller amount of the additional vinyl monomercopolymerizable with the methacrylic acid ester is more preferred, andthis additional vinyl monomer may not be used.

The weight-average molecular weight of the polymer (I) as measured byGPC is preferably 5000 to 50000, more preferably 10000 to 45000, furtherpreferably 18000 to 42000, still further preferably 20000 to 40000, fromthe viewpoint of the suppression of problems, such as silver, associatedwith molding, polymerization stability, and flowability.

The weight-average molecular weight of the polymer (I) can becontrolled, as mentioned above, by using a chain transfer agent and aniniferter, adjusting the amounts of these agents, or appropriatelychanging polymerization conditions.

The polymer (II) is preferably a polymer comprising 80 to 99.9% by massof a methacrylic acid ester monomer unit and 0.1 to 20% by mass of amonomer unit constituted by at least one additional vinyl monomercopolymerizable with the methacrylic acid ester.

The ratios of the monomer units constituting the polymer (II) can becontrolled by adjusting the amounts of the monomers added in thepolymerization step for the polymer (II) in the multistagepolymerization.

The weight-average molecular weight of the polymer (II) as measured byGPC is preferably 60000 to 350000, more preferably 100000 to 320000,further preferably 130000 to 300000, still further preferably 150000 to270000, still further preferably 170000 to 270000, from the viewpoint ofsolvent resistance and flowability.

The abundance of the component having a molecular weight of 250000 orhigher in the methacrylic resin contained in the methacrylic resincomposition of the present embodiment can be controlled by adjusting theratios of the monomer units in the polymer (II) in the multistagepolymerization mentioned above, or the weight-average molecular weightof the polymer (II).

The weight-average molecular weight of the polymer (II) can becontrolled, as mentioned above, by using a chain transfer agent and aniniferter, adjusting the amounts of these agents, or appropriatelychanging polymerization conditions.

In the first-stage polymerization step, a methacrylic acid ester monomeris used in polymerization, either alone or together with at least oneadditional vinyl monomer copolymerizable with the methacrylic acidester, to produce the polymer (I).

In the second-stage polymerization step, a methacrylic acid estermonomer and at least one additional vinyl-based monomer copolymerizablewith the methacrylic acid ester are added in the presence of the polymer(I) to produce the polymer (II). This polymerization method easilycompositionally controls each of the polymer (I) and the polymer (II)and can suppress a rise in temperature caused by the generation ofpolymerization heat during the polymerization and stabilize the internalviscosity of the system.

In this case, the partial polymerization of the composition mixture ofthe raw materials for the polymer (II) may be started before thecompletion of the polymerization for the polymer (I). It is morepreferred to temporarily perform curing (in this case, to keep theinside of the system at a temperature higher than the polymerizationtemperature) to complete the polymerization, followed by the addition ofthe composition mixture of the raw materials for the polymer (II).

The curing in the first stage not only completes the polymerization butcan remove or deactivate unreacted monomers, initiator, chain transferagent, and the like, which therefore have no adverse effect on thesecond-stage polymerization. As a result, the weight-average molecularweight of interest can be obtained.

Each polymerization temperature can be appropriately selected as theoptimum polymerization temperature for production according to thepolymerization method and is preferably 50° C. or higher and 100° C. orlower, more preferably 60° C. or higher and 90° C. or lower.

The polymerization temperatures for the polymer (I) and the polymer (II)may be the same or different.

The temperature reached by elevation for the curing is preferably atleast 5° C., more preferably at least 7° C., further preferably at least10° C., higher than the polymerization temperature for the polymer (I).

The time for which the inside of the system is kept at the temperatureis preferably 10 minutes or longer and 180 minutes or shorter, morepreferably 15 minutes or longer and 150 minutes or shorter.

Examples of the method for producing the methacrylic resin having anextrapolated onset temperature (° C.) of 120° C. or lower as determinedfrom a glass transition curve obtained by heating from 40° C. to 210° C.at a heating rate of 10° C./min according to JIS-K-7121 with α-aluminaas a reference in a nitrogen gas atmosphere using a differentialscanning calorimeter (DSC) include a method of adjusting thecopolymerization ratio of the additional vinyl monomer copolymerizablewith the methacrylic acid ester monomer mentioned above.

(Melt Flow Rate of Methacrylic Resin Composition)

The methacrylic resin composition for non-contact hot plate welding ofthe present embodiment has a melt flow rate (MFR) of 2.5 g/10 min orlower, preferably 2.2 g/10 min or lower, more preferably 2.0 g/10 min orlower and 0.1 g/10 min or higher, further preferably 1.5 g/10 min orlower and 0.2 g/10 min or higher, still further preferably 1.3 g/10 minor lower and 0.3 g/10 min or higher, under conditions of 230° C. and aload of 3.8 kg.

When MFR is 2.5 g/10 min or lower, the generation of bubbles, etc., inthe methacrylic resin composition is effectively suppressed duringmelting in the non-contact hot plate welding method.

For controlling the melt flow rate of the methacrylic resin compositionfor non-contact hot plate welding of the present embodiment to 2.5 g/10min or lower under conditions of 230° C. and a load of 3.8 kg, aneffective method involves, for example, controlling the compositionalratios of the monomer units as mentioned above, or adjusting themolecular weight, the molecular weight distribution, the abundance ofthe component having a molecular weight that is 5 times or more lowerthan a peak top molecular weight (Mp), and the abundance of thecomponent having a molecular weight of 250000 or higher.

(Other Materials)

The methacrylic resin composition of the present embodiment can be usedin combination with conventional materials known in the art mentionedlater without impairing the effects of the present invention.

<Other Resins>

Other resins to be used are not particularly limited, and a curableresin and a thermoplastic resin known in the art are preferably used.

Examples of the thermoplastic resin include, but are not limited to,polypropylene-based resins, polyethylene-based resins, polystyrene-basedresins, syndiotactic polystyrene-based resins, ABS-based resins(acrylonitrile-butadiene-styrene-based copolymers), methacrylic resins,AS-based resins (acrylonitrile-styrene-based copolymers), BAAS-basedresins (butadiene-acrylonitrile-acrylonitrile rubber-styrene-basedcopolymers, MBS-based resins (methylmethacrylate-butadiene-styrene-based copolymers), AAS-based resins(acrylonitrile-acrylonitrile rubber-styrene-based copolymers),biodegradable resins, polycarbonate-ABS resin alloys, polyalkylenearylate-based resins such as polybutylene terephthalate, polyethyleneterephthalate, polypropylene terephthalate, polytrimethyleneterephthalate, and polyethylene naphthalate, polyamide-based resins,polyphenylene ether-based resins, polyphenylene sulfide-based resins,and phenol-based resins.

Particularly, AS resins and BAAS resins are preferred for improvingflowability, ABS resins and MBS resins are preferred for improvingimpact resistance, and polyester resins are preferred for improvingchemical resistance.

Also, polyphenylene ether-based resins, polyphenylene sulfide-basedresins, phenol-based resins, and the like can be expected to produce theeffect of improving flame retardance.

Examples of the curable resin include unsaturated polyester resins,vinyl ester resins, diallyl phthalate resins, epoxy resins, cyanateresins, xylene resins, triazine resins, urea resins, melamine resins,benzoguanamine resins, urethane resins, oxetane resins, ketone resins,alkyd resins, furan resins, styrylpyridine resins, silicon resins, andsynthetic rubbers.

Only one of these resins may be used alone, or two or more of theseresins may be used in combination.

<Other Additives that can be Mixed into Methacrylic Resin Composition>

The methacrylic resin composition of the present embodiment may containan additional additive other than other resins mentioned above withoutimpairing the object of the present invention.

The methacrylic resin composition of the present embodiment isparticularly preferably supplemented with a heat stabilizer, anultraviolet absorber, and a flame retardant, etc.

<Heat stabilizer>

Examples of the heat stabilizer include, but are not limited to,antioxidants such as hindered phenol-based antioxidants andphosphorus-based processing stabilizers. A hindered phenol-basedantioxidant is preferred.

Specific examples thereof include pentaerythritoltetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate,thiodiethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate,octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate,N,N′-hexane-1,6-diylbis[3-(3,5-di-tert-butyl-4-hydroxyphenylpropionamide,3,3′,3″,5,5′,5″-hexa-tert-butyl-a,a′,a″-(mesitylene-2,4,6-triyl)tri-p-cresol,4,6-bis(octylthiomethyl)-o-cresol, 4,6-bis(dodecylthiomethyl)-o-cresol,ethylenebis(oxyethylene)bis[3-(5-tert-butyl-4-hydroxy-m-tolyl)propionate,hexamethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate,1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione,1,3,5-tris[(4-tert-butyl-3-hydroxy-2,6-xylyl)methyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione,and2,6-di-tert-butyl-4-(4,6-bis(octylthio)-1,3,5-triazin-2-ylamine)phenol.Preferred examples of the heat stabilizer include pentaerythritoltetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate.

<Ultraviolet Absorber>

Examples of the ultraviolet absorber include, but are not limited to,benzotriazole-based compounds, benzotriazine-based compounds,benzoate-based compounds, benzophenone-based compounds,oxybenzophenone-based compounds, phenol-based compounds, oxazole-basedcompounds, malonic acid ester-based compounds, cyanoacrylate-basedcompounds, lactone-based compounds, salicylic acid ester-basedcompounds, and benzoxazinone-based compounds. A benzotriazole-basedcompound or a benzotriazine-based compound is preferred.

Only one of these ultraviolet absorbers may be used alone, or two ormore thereof may be used in combination.

In the case of adding the ultraviolet absorber, its vapor pressure (P)at 20° C. is preferably 1.0×10⁻⁴ Pa or lower, more preferably 1.0×10⁻⁶Pa or lower, further preferably 1.0×10⁻⁸ Pa or lower, from the viewpointof molding processability.

The excellent molding processability means that, for example, theultraviolet absorber is less attached to mold surface during injectionmolding or is less attached to a roll during film formation.

The ultraviolet absorber attached to a roll might deteriorate, forexample, appearance or optical properties due to its attachment tomolded article surface and is therefore not preferred when the moldedarticle is used as an optical material.

The melting point (Tm) of the ultraviolet absorber is preferably 80° C.or higher, more preferably 100° C. or higher, further preferably 130° C.or higher, still further preferably 160° C. or higher.

The rate of decrease in the weight of the ultraviolet absorber byheating from 23° C. to 260° C. at a rate of 20° C./min is preferably 50%or less, more preferably 30% or less, further preferably 15% or less,still further preferably 10% or less, still further preferably 5% orless.

<Flame Retardant>

Examples of the flame retardant include, but are not limited to, cyclicnitrogen compounds, phosphorus-based flame retardants, silicon-basedflame retardants, polyhedral oligomeric silsesquioxane or partiallycleaved structures thereof, and silica-based flame retardants.

<Additional Additive Other Than Those Described Above>

The methacrylic resin composition for non-contact hot plate welding ofthe present embodiment can be further supplemented with variousadditives without impairing the effects of the present invention, fromthe viewpoint of imparting thereto other properties such as mold releaseproperties, antistatic performance, rigidity, and dimensional stability.

Examples of the additional additives include, but are not limited to:plasticizers such as phthalic acid esters, fatty acid esters,trimellitic acid esters, phosphoric acid esters, and polyesters; moldrelease agents such as higher fatty acid, higher fatty acid ester, andmono-, di-, or triglycerides of higher fatty acid; antistatic agentssuch as polyethers, polyether esters, polyether ester amides, alkylsulfonate, and alkyl benzenesulfonate; stabilizers such as antioxidantsand light stabilizers; and others such as flame retardant promoters,curing agents, curing accelerators, conductivity-imparting agents,stress releasers, crystallization accelerators, hydrolysis inhibitors,lubricants, impact modifiers, slidability-improving agents,compatibilizing agents, nucleating agents, toughening agents,strengthening agents, flow adjusters, sensitizing materials, thickeners,antisettling agents, anti-sagging agents, fillers, antifoaming agents,coupling agents, anticorrosive agents, antibacterial or antifungalagents, anti-fouling agents, and conductive polymers.

(Method for Producing Methacrylic Resin Composition)

The methacrylic resin composition for non-contact hot plate welding ofthe present embodiment can be produced by mixing the methacrylic resinmentioned above and other optional materials.

A conventional method known in the art can be used as a kneading methodfor mixing the methacrylic resin with other resins, various additives,and the like mentioned above, without particular limitations.

For example, a kneading machine such as an extruder, a heat roll, akneader, a roller mixer, or a Banbury mixer can be used in the kneadingfor production. Among them, kneading using an extruder is preferred interms of productivity.

The kneading temperature can follow the preferred processingtemperatures of the methacrylic resin constituting the thermoplasticresin composition of the present embodiment and other resins to be mixedtherewith and is in the range of preferably 140 to 300° C., morepreferably 160 to 290° C., further preferably 180 to 280° C.

(Purpose of Methacrylic Resin Composition for Non-Contact Hot PlateWelding)

The methacrylic resin composition for non-contact hot plate welding ofthe present embodiment can be suitably used for any purpose as long asthe non-contact hot plate welding method is used for the purpose.

Examples of the purpose include, but are not limited to, householdgoods, office automation equipment, audiovisual equipment, cell orelectrical components, lighting equipment, vehicle purposes, housingpurposes, sanitary purposes, amusement machines using elastic balls,liquid-crystal displays, lenses, and touch panels. Also, the methacrylicresin composition of the present embodiment can be suitably used in, forexample, transparent substrates for use in solar cells. In addition, themethacrylic resin composition of the present embodiment can also be usedin waveguides, lenses, optical fibers, covering materials for opticalfibers, LED lenses, lens covers, and the like in the fields of opticalcommunication systems, optical switching systems, and opticalmeasurement systems.

The methacrylic resin composition of the present embodiment isparticularly suitable for a member for vehicles required to havefavorable appearance traits and, specifically, preferably used inbumpers, radiator grills, visors, taillight covers, headlight covers,and meter panels, etc.

These members may be appropriately subjected to, for example, surfacefunctionalization treatment such as hard coat treatment, antireflectiontreatment, transparent conducting treatment, electromagnetic cutofftreatment, or gas barrier treatment.

[Molded Article]

The molded article of the present embodiment comprises a molded article(A) welded with an additional molded article (B),

the molded article (A) comprising a methacrylic resin comprising 80 to99.9% by mass of a methacrylic acid ester monomer unit and 0.1 to 20% bymass of a unit of at least one additional vinyl monomer copolymerizablewith the methacrylic acid ester monomer, wherein

the molded article (A) has a melt flow rate (MFR) of 2.5 g/10 min orlower at 230° C. at a load of 3.8 kg.

The molded article (A) constituting the molded article of the presentembodiment can be produced by molding the methacrylic resin compositionof the present embodiment containing the methacrylic resin mentionedabove.

The methacrylic resin contained in the molded article (A) preferably hasa weight-average molecular weight of 300000 or lower as measured by gelpermeation chromatography (GPC) and contains 6 to 50% of a componenthaving a molecular weight that is 5 times or more lower than a peak topmolecular weight (Mp) obtained from a GPC elution curve, as described inthe paragraph (Methacrylic resin).

In the methacrylic resin contained in the molded article (A), anabundance of a component having a molecular weight of 250000 or higherobtained from the GPC elution curve is preferably 12% or more of a GPCarea, as described in the paragraph (Methacrylic resin).

The methacrylic resin contained in the molded article (A) preferably hasan extrapolated onset temperature (° C.) of 120° C. or lower asdetermined from a glass transition curve obtained by heating from 40° C.to 210° C. at a heating rate of 10° C./min according to JIS-K-7121 withα-alumina as a reference in a nitrogen gas atmosphere using adifferential scanning calorimeter (DSC), as described in the paragraph(Methacrylic resin).

(Water Absorption Rate of Molded Article (A))R

The water absorption rate of the molded article (A) is preferably 0.5%by mass or lower.

The methacrylic resin is a water-absorbing resin. Therefore, the waterabsorption rate of the molded article of the methacrylic resincomposition varies depending on the management state of the moldedarticle.

Too high water absorption rate of the molded article (A) in theproduction of the molded article of the present embodiment bynon-contact hot plate welding might induce bubble generation during thewelding. Depending on the management state, it is therefore preferred tocontrol the water absorption rate.

For obtaining the stable water absorption rate in any management state,it is preferred to perform humidity control under predeterminedconditions after drying for a given time.

The water absorption rate of the molded article (A) is preferably 0.5%by mass or lower as described above, more preferably 0.4% by mass orlower, further preferably 0.3% by mass or lower. Also, the waterabsorption rate of the molded article (A) is preferably 0.001% by massor higher, more preferably 0.005% by mass or higher, further preferably0.01% by mass or higher.

The non-contact hot plate welding method may be carried out by dryingthe molded article (A) and performing humidity control so that the waterabsorption rate of the molded article (A) is adjusted to 0.5% by mass orlower. In such a case, bubble generation tends to be further suppressed.

The water absorption rate of 0.001% by mass or higher is preferredbecause the water absorption rate is easily adjusted.

Examples of the method for adjusting the water absorption rate include amethod which involves drying methacrylic resin pellets at 80° C. for 3hours and then performing a molding process at a predeterminedtemperature, followed by humidity control for 48 hours under conditionsof 23° C. and 50% RH.

Any method may be used as a method for measuring the water absorptionrate as long as the method is a general measurement method. Examplesthereof include Karl Fischer measurement and measurement using amoisture meter.

(Purpose of Molded Article)

Examples of the purpose of the molded article of the present embodimentinclude, but are not limited to, household goods, office automationequipment, audiovisual equipment, cell or electrical components,lighting equipment, vehicle purposes, housing purposes, sanitarypurposes, amusement machines using elastic balls, liquid-crystaldisplays, lenses, and touch panels. Also, the molded article of thepresent embodiment can be suitably used in, for example, transparentsubstrates for use in solar cells.

In addition, the molded article of the present embodiment can also beused in waveguides, lenses, optical fibers, covering materials foroptical fibers, LED lenses, lens covers, and the like in the fields ofoptical communication systems, optical switching systems, and opticalmeasurement systems.

The molded article of the present embodiment is particularly suitablefor a member for vehicles required to have favorable appearance traitsand, specifically, preferably used in bumpers, radiator grills, visors,taillight covers, headlight covers, and meter panels, etc.

These members may be appropriately subjected to, for example, surfacefunctionalization treatment such as hard coat treatment, antireflectiontreatment, transparent conducting treatment, electromagnetic cutofftreatment, or gas barrier treatment.

(Method for Producing Molded Article)

Examples of the method for obtaining the molded article (A) by moldingthe methacrylic resin composition of the present embodiment include, butare not limited to, molding methods in a melted state, such as injectionmolding, sheet molding, blow molding, injection blow molding, inflationmolding, T-die molding, press molding, and extrusion molding. Afabricating method such as pressure forming or vacuum forming can alsobe used.

Alternatively, an applicable method involves producing the methacrylicresin composition by kneading using a kneading machine such as a heatroll, a kneader, a Banbury mixer, or an extruder, followed by cooling,pulverization, and molding by transfer molding, injection molding,compression molding, or the like.

The order in which each of the components contained in the methacrylicresin composition is mixed is not particularly limited as long as themethod can achieve the effects of the present invention.

The additional molded article (B) other than the molded article (A),constituting the molded article of the present embodiment can also beproduced by molding in the same way as in the molded article (A) using aconventional resin known in the art, for example, an ABS-based resin.

The method for producing the molded article of the present embodimentcomprises the steps of:

heating a molded article (A) in no contact with a hot plate so that asurface of the molded article (A) is melted, the molded article (A)comprising a methacrylic resin comprising 80 to 99.9% by mass of amethacrylic acid ester monomer unit and 0.1 to 20% by mass of a unit ofat least one additional vinyl monomer copolymerizable with themethacrylic acid ester monomer, wherein the molded article (A) has amelt flow rate (MFR) of 2.5 g/10 min or lower at 230° C. at a load of3.8 kg; and

welding the molded article (A) with an additional molded article (B).

A molded article of the methacrylic resin composition of the presentembodiment can be used as the molded article (A), and a molded articleof a conventional resin known in the art can be used as the moldedarticle (B). For example, a molded article of an ABS-based resin ispreferably used as the molded article (B).

Stainless, iron, aluminum, copper, or the like can be used as the hotplate though the hot plate is not limited thereto.

Stainless is preferred from the viewpoint of durability, heatresistance, and heat conductivity.

The temperature of the hot plate is preferably 350° C. to 800° C., morepreferably 400° C. to 700° C., further preferably 450° C. to 600° C.

Examples of the method for heating the molded article (A) in no contactwith a hot plate so that its surface is melted include a method using aheater and a high-frequency induction heating method.

Examples of the method for welding the molded article (A) with anadditional molded article (B) include the method of the presentinvention as well as contact hot plate welding, vibration welding, laserwelding, and hot-melt adhesion. The non-contact hot plate welding methodis preferred in terms of weld appearance.

The methacrylic resin contained in the molded article (A) is preferablya methacrylic resin which has a weight-average molecular weight of300000 or lower as measured by gel permeation chromatography (GPC) andcontains 6 to 50% of a component having a molecular weight that is 5times or more lower than a peak top molecular weight (Mp) obtained froma GPC elution curve, as described in the paragraph (Methacrylic resin).

The methacrylic resin contained in the molded article (A) is preferablya methacrylic resin in which the abundance of a component having amolecular weight of 250000 or higher obtained from the GPC elution curveis 12% or more of the GPC area, as described in the paragraph(Methacrylic resin).

The methacrylic resin contained in the molded article (A) preferably hasan extrapolated onset temperature (° C.) of 120° C. or lower asdetermined from a glass transition curve obtained by heating from 40° C.to 210° C. at a heating rate of 10° C./min according to JIS-K-7121 withα-alumina as a reference in a nitrogen gas atmosphere using adifferential scanning calorimeter (DSC), as described in the paragraph(Methacrylic resin).

The molded article (A) preferably has a water absorption rate of 0.5% bymass or lower as described in the paragraph (Water absorption rate ofmolded article (A)).

EXAMPLES

Hereinafter, the present embodiment will be described with reference tospecific Examples and Comparative Examples. However, the presentembodiment is not intended to be limited by Examples mentioned later.

[Raw Materials used in Examples and Comparative Examples]

-   Methyl methacrylate (MMA): manufactured by Asahi Kasei Chemicals    Corp. (supplemented with 2.5 ppm of 2,4-di-methyl-6-tert-butylphenol    manufactured by CBC Co., Ltd. as a polymerization inhibitor)-   Methyl acrylate (MA): manufactured by Mitsubishi Chemical Corp.    (supplemented with 14 ppm of 4-methoxyphenol manufactured by    Kawaguchi Chemical Industry Co., Ltd. as a polymerization inhibitor)-   Ethyl acrylate (EA): manufactured by Mitsubishi Chemical Corp.-   Styrene (St): manufactured by Asahi Kasei Chemicals Corp.-   N-Phenylmaleimide (N-PhMI): manufactured by Nippon Shokubai Co.,    Ltd.-   n-Octylmercaptan: manufactured by Arkema, Inc.-   2-Ethylhexyl thioglycolate: manufactured by Arkema, Inc.-   Lauroyl peroxide: manufactured by NOF Corp.-   Calcium phosphate: manufactured by Nippon Chemical Industrial Co.,    Ltd., used as a suspending agent-   Calcium carbonate: manufactured by Shiraishi Kogyo Kaisha, Ltd.,    used as a suspending agent-   Sodium lauryl sulfate: manufactured by Wako Pure Chemical    Industries, Ltd., used as a suspension aid

[Measurement Method] (I. Composition of Methacrylic Resin andMeasurement of Molecular Weight) <1. Compositional Analysis ofMethacrylic Resin>

The compositional analysis of the methacrylic resin was conducted bypyrolysis gas chromatography and mass spectrometry.

Pyrolysis apparatus: Py-2020D manufactured by Frontier Laboratories Ltd.

Column: DB-1 (length: 30 m, inside diameter: 0.25 mm, liquid-phasethickness: 0.25 μm)

Column temperature program: kept at 40° C. for 5 min, then heated to320° C. at a rate of 50° C./min, and kept at 320° C. for 4.4 min

Pyrolytic furnace temperature: 550° C.

Column inlet temperature: 320° C.

Gas chromatography: GC6890 manufactured by Agilent Technologies, Inc.

Carrier: pure nitrogen, flow rate: 1.0 mL/min

Injection method: split method (split ratio: 1/200)

Detector: mass spectrometer Automass Sun manufactured by JEOL Ltd.

Detection method: electron impact ionization method (ion sourcetemperature: 240° C., interface temperature: 320° C.)

Sample: 10 μL of a solution of 0.1 g of the methacrylic resin in 10 ccof chloroform

The sample was collected into a platinum sample cup for the pyrolysisapparatus and dried in vacuum at 150° C. for 2 hours. Then, the samplecup was placed in the pyrolytic furnace, followed by the compositionalanalysis of the sample under the conditions described above.

The compositional ratio of the methacrylic resin was determined on thebasis of the peak areas of methyl methacrylate and methyl acrylate ontotal ion chromatography (TIC) and a calibration curve of standardsamples given below.

Preparation of standard samples for the calibration curve: 0.25% by massof lauroyl peroxide and 0.25% by mass of n-octylmercaptan were added to50 g each of a total of 5 solutions having a ratio between methylmethacrylate and methyl acrylate of (methyl methacrylate/methylacrylate)=(100% by mass/0% by mass), (98% by mass/2% by mass), (94% bymass/6% by mass), (90% by mass/10% by mass), and (80% by mass/20% bymass), respectively. Each of these mixed solutions was placed in a100-mL glass ampule, which was sealed after replacement of air withnitrogen.

The glass ampule was placed in a water bath of 80° C. for 3 hours andthen in an oven of 150° C. for 2 hours.

After cooling to room temperature, the glass was broken, and themethacrylic resin was taken out thereof and subjected to thecompositional analysis.

A graph of (Area value of methyl acrylate)/(Area value of methylmethacrylate+Area value of methyl acrylate) obtained by the measurementof the standard samples for the calibration curve and the charging ratioof methyl acrylate was used as the calibration curve.

Also, the ratios of ethyl acrylate, styrene, and N-phenylmaleimide usedas raw materials for the methacrylic resin were compositionally analyzedin the same way as in the use of methyl acrylate as a raw material asmentioned above.

<2. Methods for measuring Mw of methacrylic resin, abundance ofcomponent having molecular weight that was 5 times or more lower thanMp, and abundance of component having molecular weight of 250000 orhigher>

The weight-average molecular weight (Mw) of the methacrylic resin andthe abundances of a component having a molecular weight that was 5 timesor more lower than a peak top molecular weight (Mp) and a componenthaving a molecular weight of 250000 or higher were measured using anapparatus and conditions given below.

Measurement apparatus: gel permeation chromatography (HLC-8320GPC)manufactured by Tosho Corp.

Column: one TSKgel SuperH2500 column, two TSKgel SuperHM-M columns, andone TSK guard column SuperH-H column connected in series

These columns elute high-molecular-weight components first and elutelow-molecular-weight components late.

Detector: RI (differential refractive) detector

Detection sensitivity: 3.0 mV/min

Column temperature: 40° C.

Sample: a solution of 0.02 g of methacrylic resin in 10 mL oftetrahydrofuran

Injection volume: 10 μL

Developing solvent: tetrahydrofuran, flow rate: 0.6 mL/min

Ten monodisperse polymethyl methacrylates having a known weight peakmolecular weight and differing in molecular weight (Polymethylmethacrylate Calibration Kit PL2020-0101 M-M-10) given below were usedas standard samples for the calibration curve.

Since the polymethyl methacrylates used as the standard samples for thecalibration curve each show a single peak, (Mp) was indicated as a peakmolecular weight and distinguished from the term “peak top molecularweight” when plurality of peaks were present.

Peak molecular weight (Mp) Standard sample 1 1,916,000 Standard sample 2625,500 Standard sample 3 298,900 Standard sample 4 138,600 Standardsample 5 60,150 Standard sample 6 27,600 Standard sample 7 10,290Standard sample 8 5,000 Standard sample 9 2,810 Standard sample 10 850

RI detection intensity at the elution time of the methacrylic resin wasmeasured under the conditions described above.

The weight-average molecular weight (Mw) of the methacrylic resin, theabundance (%) of the component having a molecular weight that was 5times or more lower than a GPC peak top molecular weight (Mp), and theabundance (%) of the component having a molecular weight of 250000 orhigher were determined on the basis of areas in the GPC elution curveand the calibration curve of the approximate equation of the 7th order.

(II. Physical Property Masurement) 1. Method for Masuring Melt Flow Rate(MFR)>

The melt flow rate of the methacrylic resin composition was measured at230° C. at a load of 3.8 kg for 10 minutes according to ISO1133.

<2. Evaluation by Non-Contact Hot Plate Welding Method (Method forMeasuring Bubble Generation)>

An evaluation test by the non-contact hot plate welding method will bedescribed with reference to FIG. 1.

FIG. 1 shows a schematic diagram of one example of the evaluation testby the non-contact hot plate welding method.

The evaluation by the non-contact hot plate welding method shown in FIG.1 employed methacrylic resins produced in <Production Examples 1 to 11>mentioned later.

First, a molded article having a strip shape of 127 mm in long side×12.7mm in short side×3.2 mm in thickness was formed from each of themethacrylic resins of Production Examples 1 to 11, followed by humiditycontrol for 48 hours under conditions of 23° C. and 50% RH to obtaintest specimen 1.

Then, as shown in FIG. 1, test specimen 1 was placed in movable fixture2 capable of moving in the upward and downward directions (in FIG. 1,directions indicated by the arrows), then moved close to hot plate 3heated to 520° C. with a clearance of 0.4 mm via the movable fixture 2,and left standing for 20 seconds. Bubble generation was evaluated.

The bubble generation was evaluated according to the following criteriafor the visual evaluation:

⊚: No bubble was visually confirmed.

◯: Small bubbles having a diameter of 1 mm or smaller were visuallyconfirmed to a small extent, but no large bubble having a diameterlarger than 1 mm was visually confirmed.

×: Bubbles having a diameter larger than 1 mm were visually confirmed.

<3. Measurement of Spiral Length>

A test was conducted to determine relative flowability on the basis ofthe distance flown by each resin in a spiral cavity having a constantcross-sectional area.

Injection molding machine: IS-100EN manufactured by Toshiba Machine Co.,Ltd.

Mold for measurement: a mold in which a groove having a depth of 2 mmand a width of 12.7 mm was cut in an Archimedes spiral shape on thesurface of the mold from the central portion of the surface

Injection conditions

Resin temperature: 250° C.

Mold temperature: 60° C.

Injection pressure: 98 MPa

Injection time: 20 sec

The resin was injected to the central portion of the mold surface underthe conditions described above.

20 seconds after the completion of the injection, the spiral moldedproduct was taken out of the mold, and the length of the spiral portionwas measured. This value was used as an index for the evaluation offlowability in the molding process.

<4. Method for Measuring Resistance to Thermal Decomposition>

To evaluate resistance to thermal decomposition, the rate of decrease inmass (%) after 8 to 15 mg of a measurement sample which was kept at 270°C. in a nitrogen atmosphere for 30 minutes was measured using TG-DTA8120 (thermogravimeter and differential thermal analyzer, manufacturedby Rigaku Co., Ltd.).

A sample having a smaller absolute value of the rate of decrease in masswas evaluated as having better resistance to thermal decomposition.

The measurement sample used was each of molded articles produced inExamples and Comparative Examples mentioned later.

<5. Method for Evaluating Meltability of Methacrylic Resin in No Contactwith Hot Plate>

In the method for evaluating the meltability of the methacrylic resin,the extrapolated onset temperature (° C.) was determined from a glasstransition curve obtained by the heating of approximately 10 mg of asample from 40° C. to 210° C. at a heating rate of 10° C./min accordingto JIS-K-7121 with α-alumina as a reference in a nitrogen gas atmosphereusing a differential scanning calorimeter (Diamond DSC manufactured byPerkinElmer Japan Co., Ltd.).

<6. Evaluation of Welded Surface>

A molded article having a strip shape of 127 mm in long side×12.7 mm inshort side×3.2 mm in thickness was prepared using an ABS-based resinmanufactured by Asahi Kasei Chemicals Corp. The end face of a moldedspecimen of the methacrylic resin melted by the method of <2. Evaluationby non-contact hot plate welding (method for measuring bubblegeneration)> mentioned above was welded with the ABS-based resin. Theweld appearance was visually evaluated according to the criteria givenbelow.

Since the methacrylic resin was transparent, the welded surface wasconfirmed from the methacrylic molded article side.

◯: The roughness of the welded surface was able to be hardly confirmed.

Δ: The roughness of the welded surface was able to be slightlyconfirmed.

×: The roughness of the welded surface was able to be confirmed.

<7. Method for Measuring Water Absorption Rate of Molded Article>

A portion of test specimen 1 produced according to the paragraph <2.Evaluation by non-contact hot plate melting method (method for measuringbubble generation)> was cut out, and its water absorption rate wasmeasured in terms of % by mass using a moisture meter FM-300(manufactured by Kett Electric Laboratory). Measurement conditions willbe described below.

Measurement principle: reference drying method by heating

Temperature: 210 ±5° C.

Nitrogen flow rate: 350 ±50 ml/min

[Production Examples of Methacrylic Resin]

The methacrylic resin used was each of resins (A-1) to (A-11) producedby Production Examples 1 to 11 described below.

Production Example 1

A container having a stirrer was charged with 2 kg of ion-exchangewater, 65 g of calcium phosphate, 39 g of calcium carbonate, and 0.39 gof sodium lauryl sulfate to obtain a mixed solution (a).

Subsequently, a 60-L reactor was charged with 26 kg of ion-exchangewater, heated to 80° C., and charged with the mixed solution (a) and21.2 kg of methyl methacrylate, 0.43 kg of methyl acrylate, 27 g oflauroyl peroxide, and 62 g of n-octylmercaptan.

Then, suspension polymerization was performed with the temperature keptat approximately 80° C. After observation of an exothermic peak, thetemperature was raised to 92° C. at a rate of 1° C./min, and the polymerwas aged for 60 minutes to substantially terminate the polymerizationreaction.

Subsequently, the reactor was cooled to 50° C. and charged with 20% bymass of sulfuric acid for the dissolution of the suspending agent. Then,the polymerization reaction solution was sifted through a 1.68-mm meshsieve to remove aggregates. The obtained polymer in the form of beadswas subjected to washing, dehydration, and drying treatments to obtainfine polymer particles.

The obtained fine polymer particles were melt-kneaded in a ϕ30 mmtwin-screw extruder set to 230° C., and the strands were cooled and cutto obtain methacrylic resin pellets (A-1).

The obtained methacrylic resin pellets had a compositional ratio ofMMA/MA=98.0/2.0 wt %, Mw of 102000, and MFR of 2.1 g/10 min.

The abundance (%) of the component having a molecular weight that was 5times or more lower than Mp was 4.5%, and the abundance (%) of thecomponent having a molecular weight of 250000 or higher was 5.0%.

The rate of decrease in mass (%) in the TG-DTA measurement was 2.0%, andthe extrapolated onset temperature (° C.) in the DSC measurement was110.5° C.

Production Example 2

A container having a stirrer was charged with 2 kg of ion-exchangewater, 65 g of calcium phosphate, 39 g of calcium carbonate, and 0.39 gof sodium lauryl sulfate to obtain a mixed solution (b).

Subsequently, a 60-L reactor was charged with 23 kg of ion-exchangewater, heated to 80° C., and charged with the mixed solution (b) and 5.5kg of methyl methacrylate, 40 g of lauroyl peroxide, and 90 g of2-ethylhexyl thioglycolate.

Then, suspension polymerization was performed with the temperature keptat approximately 80° C. After observation of an exothermic peak, thetemperature was raised to 92° C. at a rate of 1° C./min, and thetemperature of 92° C. to 94° C. was maintained for 30 minutes. Then, thetemperature was dropped to 80° C. at a rate of 1° C./min. Subsequently,the reactor was charged with 16.2 kg of methyl methacrylate, 0.75 kg ofmethyl acrylate, 21 g of lauroyl peroxide, and 17.5 g ofn-octylmercaptan. Subsequently, suspension polymerization was performedwith the temperature kept at approximately 80° C.

After observation of an exothermic peak, the temperature was raised to92° C. at a rate of 1° C./min, and the polymer was then aged for 60minutes to substantially terminate the polymerization reaction.

Subsequently, the reactor was cooled to 50° C. and charged with 20% bymass of sulfuric acid for the dissolution of the suspending agent. Then,the polymerization reaction solution was sifted through a 1.68-mm meshsieve to remove aggregates. The obtained polymer in the form of beadswas subjected to washing, dehydration, and drying treatments to obtainfine polymer particles.

The obtained fine polymer particles were melt-kneaded in a ϕ30 mmtwin-screw extruder set to 240° C., and the strands were cooled and cutto obtain methacrylic resin pellets (A-2).

The obtained methacrylic resin pellets had a compositional ratio ofMMA/MA=96.7/3.3 wt %, Mw of 172000, and MFR of 0.53 g/10 min.

The abundance (%) of the component having a molecular weight that was 5times or more lower than Mp was 24.5%, and the abundance (%) of thecomponent having a molecular weight of 250000 or higher was 23%.

The rate of decrease in mass (%) in the TG-DTA measurement was 2.3%, andthe extrapolated onset temperature (° C.) in the DSC measurement was107.1° C.

Production Example 3

A container having a stirrer was charged with 2 kg of ion-exchangewater, 65 g of calcium phosphate, 39 g of calcium carbonate, and 0.39 gof sodium lauryl sulfate to obtain a mixed solution (c).

Subsequently, a 60-L reactor was charged with 23 kg of ion-exchangewater, heated to 80° C., and charged with the mixed solution (c) and 6.6kg of methyl methacrylate, 0.13 kg of methyl acrylate, 40 g of lauroylperoxide, and 135 g of 2-ethylhexyl thioglycolate.

Then, suspension polymerization was performed with the temperature keptat approximately 80° C. After observation of an exothermic peak, thetemperature was raised to 92° C. at a rate of 1° C./min, and thetemperature of 92° C. to 94° C. was maintained for 30 minutes. Then, thetemperature was dropped to 80° C. at a rate of 1° C./min. Subsequently,the reactor was charged with 15.9 kg of methyl methacrylate, 0.63 kg ofmethyl acrylate, 30 g of lauroyl peroxide, and 20 g of n-octylmercaptan.Subsequently, suspension polymerization was performed with thetemperature kept at approximately 80° C.

After observation of an exothermic peak, the temperature was raised to92° C. at a rate of 1° C./min, and the polymer was then aged for 60minutes to substantially terminate the polymerization reaction.

Subsequently, the reactor was cooled to 50° C. and charged with 20% bymass of sulfuric acid for the dissolution of the suspending agent. Then,the polymerization reaction solution was sifted through a 1.68-mm meshsieve to remove aggregates. The obtained polymer in the form of beadswas subjected to washing, dehydration, and drying treatments to obtainfine polymer particles.

The obtained fine polymer particles were melt-kneaded in a ϕ30 mmtwin-screw extruder set to 240° C., and the strands were cooled and cutto obtain methacrylic resin pellets (A-3).

The obtained methacrylic resin pellets had a compositional ratio ofMMA/MA=96.5/3.5 wt %, Mw of 135000, and MFR of 1.1 g/10 min.

The abundance (%) of the component having a molecular weight that was 5times or more lower than Mp was 28.5%, and the abundance (%) of thecomponent having a molecular weight of 250000 or higher was 17.5%.

The rate of decrease in mass (%) in the TG-DTA measurement was 2.5%, andthe extrapolated onset temperature (° C.) in the DSC measurement was107.5° C.

Production Example 4

A container having a stirrer was charged with 2 kg of ion-exchangewater, 65 g of calcium phosphate, 39 g of calcium carbonate, and 0.39 gof sodium lauryl sulfate to obtain a mixed solution (d).

Subsequently, a 60-L reactor was charged with 23 kg of ion-exchangewater, heated to 80° C., and charged with the mixed solution (d) and 7.8kg of methyl methacrylate, 0.16 kg of methyl acrylate, 55 g of lauroylperoxide, and 165 g of 2-ethylhexyl thioglycolate.

Then, suspension polymerization was performed with the temperature keptat approximately 80° C. After observation of an exothermic peak, thetemperature was raised to 92° C. at a rate of 1° C./min, and thetemperature of 92° C. to 94° C. was maintained for 30 minutes. Then, thetemperature was dropped to 80° C. at a rate of 1° C./min. Subsequently,the reactor was charged with 15.0 kg of methyl methacrylate, 0.3 kg ofmethyl acrylate, 25 g of lauroyl peroxide, and 18.5 g ofn-octylmercaptan. Subsequently, suspension polymerization was performedwith the temperature kept at approximately 80° C.

After observation of an exothermic peak, the temperature was raised to92° C. at a rate of 1° C./min, and the polymer was then aged for 60minutes to substantially terminate the polymerization reaction.

Subsequently, the reactor was cooled to 50° C. and charged with 20% bymass of sulfuric acid for the dissolution of the suspending agent. Then,the polymerization reaction solution was sifted through a 1.68-mm meshsieve to remove aggregates. The obtained polymer in the form of beadswas subjected to washing, dehydration, and drying treatments to obtainfine polymer particles.

The obtained fine polymer particles were melt-kneaded in a ϕ30 mmtwin-screw extruder set to 230° C., and the strands were cooled and cutto obtain methacrylic resin pellets (A-4).

The obtained methacrylic resin pellets had a compositional ratio ofMMA/MA=98.1/1.9 wt %, Mw of 127000, and MFR of 1.5 g/10 min.

The abundance (%) of the component having a molecular weight that was 5times or more lower than Mp was 32.5%, and the abundance (%) of thecomponent having a molecular weight of 250000 or higher was 16.5%.

The rate of decrease in mass (%) in the TG-DTA measurement was 2.9%, andthe extrapolated onset temperature (° C.) in the DSC measurement was107.3° C.

Production Example 5

A container having a stirrer was charged with 2 kg of ion-exchangewater, 65 g of calcium phosphate, 39 g of calcium carbonate, and 0.39 gof sodium lauryl sulfate to obtain a mixed solution (e).

Subsequently, a 60-L reactor was charged with 26 kg of ion-exchangewater, heated to 80° C., and charged with the mixed solution (e) and21.3 kg of methyl methacrylate, 2.3 kg of methyl acrylate, 65 g oflauroyl peroxide, and 70 g of n-octylmercaptan.

Then, suspension polymerization was performed with the temperature keptat approximately 80° C. After observation of an exothermic peak, thetemperature was raised to 92° C. at a rate of 1° C./min, and the polymerwas aged for 60 minutes to substantially terminate the polymerizationreaction.

Subsequently, the reactor was cooled to 50° C. and charged with 20% bymass of sulfuric acid for the dissolution of the suspending agent. Then,the polymerization reaction solution was sifted through a 1.68-mm meshsieve to remove aggregates. The obtained polymer in the form of beadswas subjected to washing, dehydration, and drying treatments to obtainfine polymer particles.

The obtained fine polymer particles were melt-kneaded in a ϕ30 mmtwin-screw extruder set to 220° C., and the strands were cooled and cutto obtain methacrylic resin pellets (A-5).

The obtained methacrylic resin pellets had a compositional ratio ofMMA/MA=90/10 wt %, Mw of 92000, and MFR of 9.0 g/10 min.

The abundance (%) of the component having a molecular weight that was 5times or more lower than Mp was 4.6%, and the abundance (%) of thecomponent having a molecular weight of 250000 or higher was 4.5%.

The rate of decrease in mass (%) in the TG-DTA measurement was 1.4%, andthe extrapolated onset temperature (° C.) in the DSC measurement was101.5° C.

Production Example 6

A container having a stirrer was charged with 2 kg of ion-exchangewater, 65 g of calcium phosphate, 39 g of calcium carbonate, and 0.39 gof sodium lauryl sulfate to obtain a mixed solution (f).

Subsequently, a 60-L reactor was charged with 23 kg of ion-exchangewater, heated to 80° C., and charged with the mixed solution (f) and 2.3kg of methyl methacrylate, 16 g of lauroyl peroxide, and 45 g of2-ethylhexyl thioglycolate.

Then, suspension polymerization was performed with the temperature keptat approximately 80° C. After observation of an exothermic peak, thetemperature was raised to 92° C. at a rate of 1° C./min, and thetemperature of 92° C. to 94° C. was then maintained for 30 minutes.Then, the temperature was dropped to 80° C. at a rate of 1° C./min.Subsequently, the reactor was charged with 19.2 kg of methylmethacrylate, 2.1 kg of methyl acrylate, 40 g of lauroyl peroxide, and45 g of n-octylmercaptan. Subsequently, suspension polymerization wasperformed with the temperature kept at approximately 80° C.

After observation of an exothermic peak, the temperature was raised to92° C. at a rate of 1° C./min, and the polymer was then aged for 60minutes to substantially terminate the polymerization reaction.

Subsequently, the reactor was cooled to 50° C. and charged with 20% bymass of sulfuric acid for the dissolution of the suspending agent. Then,the polymerization reaction solution was sifted through a 1.68-mm meshsieve to remove aggregates. The obtained polymer in the form of beadswas subjected to washing, dehydration, and drying treatments to obtainfine polymer particles.

The obtained fine polymer particles were melt-kneaded in a ϕ30 mmtwin-screw extruder set to 230° C., and the strands were cooled and cutto obtain methacrylic resin pellets (A-6).

The obtained methacrylic resin pellets had a compositional ratio ofMMA/MA=91.0/9.0 wt %, Mw of 116000, and MFR of 4.5 g/10 min.

The abundance (%) of the component having a molecular weight that was 5times or more lower than Mp was 7.9%, and the abundance (%) of thecomponent having a molecular weight of 250000 or higher was 8.1%.

The rate of decrease in mass (%) in the TG-DTA measurement was 1.6%, andthe extrapolated onset temperature (° C.) in the DSC measurement was102.3° C.

Production Example 7

A container having a stirrer was charged with 2 kg of ion-exchangewater, 65 g of calcium phosphate, 39 g of calcium carbonate, and 0.39 gof sodium lauryl sulfate to obtain a mixed solution (g).

Subsequently, a 60-L reactor was charged with 23 kg of ion-exchangewater, heated to 80° C., and charged with the mixed solution (g) and7.96 kg of methyl methacrylate, 55 g of lauroyl peroxide, and 165 g of2-ethylhexyl thioglycolate.

Then, suspension polymerization was performed with the temperature keptat approximately 80° C. After observation of an exothermic peak, thetemperature was raised to 92° C. at a rate of 1° C./min, and thetemperature of 92° C. to 94° C. was maintained for 30 minutes. Then, thetemperature was dropped to 80° C. at a rate of 1° C./min. Subsequently,the reactor was charged with 15.0 kg of methyl methacrylate, 0.2 kg ofstyrene, 0.1 kg of N-phenylmaleimide, 25 g of lauroyl peroxide, and 18.5g of n-octylmercaptan. Subsequently, suspension polymerization wasperformed with the temperature kept at approximately 80° C.

After observation of an exothermic peak, the temperature was raised to92° C. at a rate of 1° C./min, and the polymer was then aged for 60minutes to substantially terminate the polymerization reaction.

Subsequently, the reactor was cooled to 50° C. and charged with 20% bymass of sulfuric acid for the dissolution of the suspending agent. Then,the polymerization reaction solution was sifted through a 1.68-mm meshsieve to remove aggregates. The obtained polymer in the form of beadswas subjected to washing, dehydration, and drying treatments to obtainfine polymer particles.

The obtained fine polymer particles were melt-kneaded in a ϕ30 mmtwin-screw extruder set to 230° C., and the strands were cooled and cutto obtain methacrylic resin pellets (A-7).

The obtained methacrylic resin pellets had a compositional ratio ofMMA/St/PhMI=98.7/0.86/0.44 wt %, Mw of 123000, and MFR of 1.4 g/10 min.

The abundance (%) of the component having a molecular weight that was 5times or more lower than Mp was 33.5%, and the abundance (%) of thecomponent having a molecular weight of 250000 or higher was 16.2%.

The rate of decrease in mass (%) in the TG-DTA measurement was 3.2%, andthe extrapolated onset temperature (° C.) in the DSC measurement was108.5° C.

Production Example 8

A container having a stirrer was charged with 2 kg of ion-exchangewater, 65 g of calcium phosphate, 39 g of calcium carbonate, and 0.39 gof sodium lauryl sulfate to obtain a mixed solution (h).

Subsequently, a 60-L reactor was charged with 23 kg of ion-exchangewater, heated to 80° C., and charged with the mixed solution (h) and 6.6kg of methyl methacrylate, 0.13 kg of ethyl acrylate, 40 g of lauroylperoxide, and 135 g of 2-ethylhexyl thioglycolate.

Then, suspension polymerization was performed with the temperature keptat approximately 80° C. After observation of an exothermic peak, thetemperature was raised to 92° C. at a rate of 1° C./rain, and thetemperature of 92° C. to 94° C. was maintained for 30 minutes. Then, thetemperature was dropped to 80° C. at a rate of 1° C./min. Subsequently,the reactor was charged with 15.9 kg of methyl methacrylate, 0.63 kg ofethyl acrylate, 30 g of lauroyl peroxide, and 20 g of n-octylmercaptan.Subsequently, suspension polymerization was performed with thetemperature kept at approximately 80° C.

After observation of an exothermic peak, the temperature was raised to92° C. at a rate of 1° C./min, and the polymer was then aged for 60minutes to substantially terminate the polymerization reaction.

Subsequently, the reactor was cooled to 50° C. and charged with 20% bymass of sulfuric acid for the dissolution of the suspending agent. Then,the polymerization reaction solution was sifted through a 1.68-mm meshsieve to remove aggregates. The obtained polymer in the form of beadswas subjected to washing, dehydration, and drying treatments to obtainfine polymer particles.

The obtained fine polymer particles were melt-kneaded in a ϕ30 mmtwin-screw extruder set to 240° C., and the strands were cooled and cutto obtain methacrylic resin pellets (A-8).

The obtained methacrylic resin pellets had a compositional ratio ofMMA/EA=96.7/3.3 wt %, Mw of 133000, and MFR of 1.0 g/10 min.

The abundance (%) of the component having a molecular weight that was 5times or more lower than Mp was 29.5%, and the abundance (%) of thecomponent having a molecular weight of 250000 or higher was 17.2%.

The rate of decrease in mass (%) in the TG-DTA measurement was 2.6%, andthe extrapolated onset temperature (° C.) in the DSC measurement was106.8° C.

Production Example 9

A container having a stirrer was charged with 2 kg of ion-exchangewater, 65 g of calcium phosphate, 39 g of calcium carbonate, and 0.39 gof sodium lauryl sulfate to obtain a mixed solution (i).

Subsequently, a 60-L reactor was charged with 23 kg of ion-exchangewater, heated to 80° C., and charged with the mixed solution (i) and7.96 kg of methyl methacrylate, 55 g of lauroyl peroxide, and 135 g of2-ethylhexyl thioglycolate.

Then, suspension polymerization was performed with the temperature keptat approximately 80° C. After observation of an exothermic peak, thetemperature was raised to 92° C. at a rate of 1° C./min, and thetemperature of 92° C. to 94° C. was maintained for 30 minutes. Then, thetemperature was dropped to 80° C. at a rate of 1° C./min. Subsequently,the reactor was charged with 11.0 kg of methyl methacrylate, 1.5 kg ofstyrene, 3.5 kg of N-phenylmaleimide, 35 g of lauroyl peroxide, and 20 gof n-octylmercaptan. Subsequently, suspension polymerization wasperformed with the temperature kept at approximately 80° C. Afterobservation of an exothermic peak, the temperature was raised to 92° C.at a rate of 1° C./min, and the polymer was then aged for 60 minutes tosubstantially terminate the polymerization reaction.

Subsequently, the reactor was cooled to 50° C. and charged with 20% bymass of sulfuric acid for the dissolution of the suspending agent. Then,the polymerization reaction solution was sifted through a 1.68-mm meshsieve to remove aggregates. The obtained polymer in the form of beadswas subjected to washing, dehydration, and drying treatments to obtainfine polymer particles.

The obtained fine polymer particles were melt-kneaded in a ϕ30 mmtwin-screw extruder set to 260° C., and the strands were cooled and cutto obtain methacrylic resin pellets (A-9).

The obtained methacrylic resin pellets had a compositional ratio ofMMA/St/N-PhMA=79/6/15 wt %, Mw of 121000, and MFR of 1.2 g/10 min.

The abundance (%) of the component having a molecular weight that was 5times or more lower than Mp was 32.5%, and the abundance (%) of thecomponent having a molecular weight of 250000 or higher was 14.5%.

The rate of decrease in mass (%) in the TG-DTA measurement was 1.2%, andthe extrapolated onset temperature (° C.) in the DSC measurement was123.2° C.

Production Example 10

A container having a stirrer was charged with 2 kg of ion-exchangewater, 65 g of calcium phosphate, 39 g of calcium carbonate, and 0.39 gof sodium lauryl sulfate to obtain a mixed solution (j).

Subsequently, a 60-L reactor was charged with 26 kg of ion-exchangewater, heated to 80° C., and charged with the mixed solution (j) and21.2 kg of methyl methacrylate, 0.43 kg of methyl acrylate, 27 g oflauroyl peroxide, and 85 g of n-octylmercaptan.

Then, suspension polymerization was performed with the temperature keptat approximately 80° C. After observation of an exothermic peak, thetemperature was raised to 92° C. at a rate of 1° C./min, and the polymerwas aged for 60 minutes to substantially terminate the polymerizationreaction.

Subsequently, the reactor was cooled to 50° C. and charged with 20% bymass of sulfuric acid for the dissolution of the suspending agent. Then,the polymerization reaction solution was sifted through a 1.68-mm meshsieve to remove aggregates. The obtained polymer in the form of beadswas subjected to washing, dehydration, and drying treatments to obtainfine polymer particles.

The obtained fine polymer particles were melt-kneaded in a ϕ30 mmtwin-screw extruder set to 230° C., and the strands were cooled and cutto obtain methacrylic resin pellets (A-10).

The obtained methacrylic resin pellets had a compositional ratio ofMMA/MA=98.0/2.0 wt %, Mw of 75000, and MFR of 3.1 g/10 min.

The abundance (%) of the component having a molecular weight that was 5times or more lower than Mp was 4.5%, and the abundance (%) of thecomponent having a molecular weight of 250000 or higher was 1.5%.

The rate of decrease in mass (%) by heat in the TG-DTA measurement was2.0%, and the extrapolated onset temperature (° C.) in the DSCmeasurement was 109.7° C.

Production Example 11

A container having a stirrer was charged with 2 kg of ion-exchangewater, 65 g of calcium phosphate, 39 g of calcium carbonate, and 0.39 gof sodium lauryl sulfate to obtain a mixed solution (k).

Subsequently, a 60-L reactor was charged with 26 kg of ion-exchangewater, heated to 80° C., and charged with the mixed solution (k) and 5.5kg of methyl methacrylate, 40 g of lauroyl peroxide, and 120 g of2-ethylhexyl thioglycolate.

Then, suspension polymerization was performed with the temperature keptat approximately 80° C. An exothermic peak was observed 90 minutes afterthe charging of the raw materials. Then, the temperature was raised to92° C. at a rate of 1° C./min, and the temperature of 92° C. to 94° C.was then maintained for 30 minutes.

Then, the temperature was dropped to 80° C. at a rate of 1° C./min.Subsequently, the reactor was charged with 16.5 kg of methylmethacrylate, 0.41 kg of methyl acrylate, 20 g of lauroyl peroxide, and30 g of n-octylmercaptan. Subsequently, suspension polymerization wasperformed with the temperature kept at approximately 80° C. Anexothermic peak was observed 95 minutes after the charging of the rawmaterials.

Then, the temperature was raised to 92° C. at a rate of 1° C./min, andthe polymer was then aged for 60 minutes to substantially terminate thepolymerization reaction.

Subsequently, the reactor was cooled to 50° C. and charged with 20% bymass of sulfuric acid for the dissolution of the suspending agent. Then,the polymerization reaction solution was sifted through a 1.68-mm meshsieve to remove aggregates. The obtained polymer in the form of beadswas subjected to washing, dehydration, and drying treatments to obtainfine polymer particles.

The obtained fine polymer particles were melt-kneaded in a ϕ30 mmtwin-screw extruder set to 230° C., and the strands were cooled and cutto obtain methacrylic resin pellets (A-11).

The obtained methacrylic resin pellets had a compositional ratio ofMMA/MA=98.1/1.9 wt %, Mw of 113000, and MFR of 1.8 g/10 min.

The abundance (%) of the component having a molecular weight that was 5times or more lower than Mp was 22.5%, and the abundance (%) of thecomponent having a molecular weight of 250000 or higher was 10.5%.

The rate of decrease in mass (%) by heat in the TG-DTA measurement was3.5%, and the extrapolated onset temperature (° C.) in the DSCmeasurement was 108.7° C.

[Examples 1 to 8] and [Comparative Examples 1 to 3]

100% by mass of the methacrylic resin obtained in each of ProductionExamples 1 to 11 was used in injection molding at 220° C. to 240° C. toproduce a molded article having a strip shape of 127 mm×12.7 mm×3.2 mmt.

After the molding, humidity control was performed by the methoddescribed in the non-contact hot plate welding method described above toadjust the water absorption rate of the molded article. Then, the waterabsorption rate was measured using a moisture meter.

The molded article (corresponding to test specimen 1) was used in theevaluation of the welded surface by the non-contact hot plate weldingmethod (evaluation of bubble generation), the measurement and evaluationof resistance to thermal decomposition, and the appearance evaluation ofthe welded surface.

As for the measurement and evaluation of the spiral length and theevaluation of the meltability of the methacrylic resin in no contactwith a hot plate (measurement of extrapolated onset temperature by TGA)as mentioned above, the methacrylic resin pellets of Production Examplesmentioned above were measured and evaluated.

The measurement results are shown in Table 1 below.

Example 9

100% by mass of the methacrylic resin pellets (A-4) of ProductionExample 4 was used in injection molding at 230° C. to produce a moldedarticle having a strip shape of 127 mm×12.7 mm×3.2 mmt.

Humidity control was performed for 240 hours under conditions of 23° C.and 50% RH to adjust the water absorption rate of the molded article.Then, the water absorption rate was measured using a moisture meter toobtain test specimen 1.

The molded article (corresponding to test specimen 1) was used in theevaluation of the welded surface by the non-contact hot plate weldingmethod (evaluation of bubble generation), the measurement and evaluationof resistance to thermal decomposition, and the appearance evaluation ofthe welded surface.

As for the measurement and evaluation of the spiral length and theevaluation of the meltability of the methacrylic resin in no contactwith a hot plate (measurement of extrapolated onset temperature by TGA)as mentioned above, the methacrylic resin pellets of Production Examplesmentioned above were measured and evaluated.

The molded article of the methacrylic resin pellets (A-4) was weldedwith a molded article of an ABS resin to prepare a welded moldedarticle.

Example 10

100% by mass of the methacrylic resin pellets (A-4) of ProductionExample 4 was used in injection molding at 230° C. to produce a moldedarticle having a strip shape of 127 mm×12.7 mm×3.2 mmt.

Humidity control was performed for 48 hours under conditions of 23° C.and 50% RH. The water absorption rate was measured using a moisturemeter to obtain test specimen 1.

Then, as shown in FIG. 1, test specimen 1 was placed in movable fixture2 capable of moving in the upward and downward directions (in FIG. 1,directions indicated by the arrows), then moved close to hot plate 3heated to 550° C. with a clearance of 0.4 mm via the movable fixture 2,and left standing for 20 seconds. Bubble generation was evaluated by themethod described in the paragraph <2. Non-contact hot plate weldingmethod>.

Also, the measurement and evaluation of resistance to thermaldecomposition and the appearance evaluation of the welded surface wereconducted.

As for the measurement and evaluation of the spiral length and theevaluation of the meltability of the methacrylic resin in no contactwith a hot plate (measurement of extrapolated onset temperature by TGA)as mentioned above, the methacrylic resin pellets of Production Examplesmentioned above were measured and evaluated.

The molded article of the methacrylic resin pellets (A-4) was weldedwith a molded article of an ABS resin to prepare a welded moldedarticle.

TABLE 1 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6Example 7 Methacrylic resin A-1 100 (mass %) A-2 100 A-3 100 A-4 100 A-5A-6 A-7 100 A-8 100 A-9 100 A-10 A-11 Evaluation by non-contact hotplate ◯ ⊚ ⊚ ⊚ ⊚ ⊚ ⊚ welding method Spiral length (cm) 26.5 27.5 31.533.5 33.0 31.0 28.5 Rate of decrease in mass (%) in TG- 2.0 2.3 2.5 2.93.2 2.6 1.2 DTA Extrapolated onset temperature (° C.) 110.5 107.1 107.5107.3 108.5 106.8 123.2 of glass transition temperature in DSCmeasurement Abundance (%) of component having 5.0 23 17.5 16.5 16.2 17.214.5 molecular weight of 250000 or higher Water absorption rate (mass %)of 0.2 0.2 0.2 0.2 0.2 0.2 0.3 molded test specimen Appearanceevaluation of welded Δ ◯ ◯ ◯ ◯ ◯ Δ surface Comparative ComparativeComparative Example 8 Example 9 Example 10 Example 1 Example 2 Example 3Methacrylic resin A-1 (mass %) A-2 A-3 A-4 100 100 A-5 100 A-6 100 A-7A-8 A-9 A-10 100 A-11 100 Evaluation by non-contact hot plate ◯ ◯ ◯ X XX welding method Spiral length (cm) 32.5 33.5 33.5 38.0 28.0 33.5 Rateof decrease in mass (%) in TG- 3.5 2.9 2.9 1.4 1.6 2.0 DTA Extrapolatedonset temperature (° C.) 108.7 107.3 107.3 101.5 102.3 109.7 of glasstransition temperature in DSC measurement Abundance (%) of componenthaving 10.5 16.5 16.5 4.5 8.1 1.5 molecular weight of 250000 or higherWater absorption rate (mass %) of 0.2 0.55 0.2 0.2 0.2 0.2 molded testspecimen Appearance evaluation of welded Δ Δ Δ X X X surface

In Example 1, because MFR was appropriate, small bubbles were confirmedonly to a small extent during melting by the non-contact hot platewelding method, and the appearance of the joined part was alsofavorable.

In Examples 2 to 4, because MFR was appropriate and the abundance (%) ofthe component having a molecular weight that was 5 times or more lowerthan a peak top molecular weight (Mp) was in a more preferred range ascompared with Example 1, no bubble or foam was confirmed during meltingby the non-contact hot plate melting method, and the appearance of thejoined part was very favorable.

In Examples 5 and 6, the methacrylic acid ester monomer wascopolymerized with a monomer other than methyl acrylate used as at leastone additional vinyl monomer copolymerizable with the methacrylic acidester monomer. However, because MFR was appropriate and the abundance(%) of the component having a molecular weight that was 5 times or morelower than a peak top molecular weight (Mp) was in a preferred range, nobubble or foam was confirmed during melting by the non-contact hot platemelting method, and the appearance of the joined part was veryfavorable.

In Example 7, the extrapolated onset temperature (° C.) of a glasstransition temperature in the DSC measurement was slightly high, and theappearance of the joined part had slight roughness as compared with theother Examples, but was sufficiently favorable for practical use.

In Example 8, the abundance (%) of the component having a molecularweight of 250000 or higher was slightly small, and small bubbles wereconfirmed to a small extent as compared with the other Examples.However, the welded molded article had a favorable level for practicaluse.

In Example 9, small bubbles were confirmed to a small extent as comparedwith the other Examples due to the influence of the increased waterabsorption rate of the molded article. However, the welded moldedarticle had a favorable level for practical use.

In Example 10, small bubbles were confirmed to a small extent ascompared with the other Examples due to the evaluation conducted at ahot plate temperature as high as 550° C. for the non-contact hot platemethod. However, the welded molded article had a favorable level forpractical use.

On the other hand, in Comparative Example 1, MFR was considerably high,and bubbles having a diameter of 1 mm or larger were generated.

In Comparative Example 2, although the abundance (%) of the componenthaving a molecular weight that was 5 times or more lower than a peak topmolecular weight (Mp) was in a preferred range, a large number ofbubbles having a diameter of 1 mm or larger were generated due to largeMFR. In addition, the appearance of the welded surface was rough due tothe influence of the bubble generation and was thus not preferred.

In Comparative Example 3, although MFR was 3.1 g/10 min which was closeto 2.5 g/10 min, bubbles having a diameter of 1 mm or larger weregenerated, and the appearance of the welded surface was also rough.

The present application is based on Japanese Patent Application No.2014-185492 filled in the Japan Patent Office on Sep. 11, 2014, thecontents of which are incorporated herein by reference.

INDUSTRIAL APPLICABILITY

The methacrylic resin composition of the present invention hasindustrial applicability as a raw material for a member for a vehicle,such as a taillight cover, a headlight cover, or a meter panel.

REFERENCE SIGNS LIST

-   1: test specimen-   2: movable fixture-   3: hot plate

1. A methacrylic resin composition for non-contact hot plate weldingcomprising a methacrylic resin comprising 80 to 99.9% by mass of amethacrylic acid ester monomer unit and 0.1 to 20% by mass of a unit ofat least one additional vinyl monomer copolymerizable with themethacrylic acid ester monomer, wherein the methacrylic resincomposition has a melt flow rate (MFR) of 2.5 g/10 min or lower at 230°C. at a load of 3.8 kg.
 2. The methacrylic resin composition fornon-contact hot plate welding according to claim 1, wherein themethacrylic resin is a methacrylic resin which has a weight-averagemolecular weight of 300000 or lower as measured by gel permeationchromatography (GPC), and contains 6 to 50% of a component having amolecular weight that is 5 times or more lower than a peak top molecularweight (Mp) obtained from a GPC elution curve.
 3. The methacrylic resincomposition for non-contact hot plate welding according to claim 1,wherein the methacrylic resin is a methacrylic resin in which anabundance of a component having a molecular weight of 250000 or higherobtained from a GPC elution curve is 12% or more of a GPC area.
 4. Themethacrylic resin composition for non-contact hot plate weldingaccording to claim 1, wherein the methacrylic resin has an extrapolatedonset temperature (° C.) of 120° C. or lower as determined from a glasstransition curve obtained by heating from 40° C. to 210° C. at a heatingrate of 10° C./min according to JIS-K-7121 with α-alumina as a referencein a nitrogen gas atmosphere using a differential scanning calorimeter(DSC). 5-6. (canceled)
 7. A molded article comprising a molded article(A) welded with an additional molded article (B), the molded article (A)comprising a methacrylic resin comprising 80 to 99.9% by mass of amethacrylic acid ester monomer unit and 0.1 to 20% by mass of a unit ofat least one additional vinyl monomer copolymerizable with themethacrylic acid ester monomer, wherein the molded article (A) has amelt flow rate (MFR) of 2.5 g/10 min or lower at 230° C. at a load of3.8 kg.
 8. The molded article according to claim 7, wherein themethacrylic resin is a methacrylic resin which has a weight-averagemolecular weight of 300000 or lower as measured by gel permeationchromatography (GPC), and contains 6 to 50% of a component having amolecular weight that is 5 times or more lower than a peak top molecularweight (Mp) obtained from a GPC elution curve.
 9. The molded articleaccording to claim 7, wherein the methacrylic resin is a methacrylicresin in which an abundance of a component having a molecular weight of250000 or higher obtained from a GPC elution curve is 12% or more of aGPC area.
 10. The molded article according to claim 7, wherein themethacrylic resin has an extrapolated onset temperature (° C.) of 120°C. or lower as determined from a glass transition curve obtained byheating from 40° C. to 210° C. at a heating rate of 10° C./min accordingto JIS-K-7121 with α-alumina as a reference in a nitrogen gas atmosphereusing a differential scanning calorimeter (DSC).
 11. The molded articleaccording to claim 7, wherein the molded article (A) has a waterabsorption rate of 0.5% by mass or lower. 12-13. (canceled)
 14. Themolded article according to claim 7, wherein the molded article (B) is amolded article of an ABS-based resin.
 15. A member for a vehicle,comprising the molded article according to claim
 7. 16. The member forthe vehicle according to claim 15, wherein the member for the vehicle isat least one member selected from the group consisting of a taillightcover, a headlight cover, and a meter panel.
 17. A method for producinga molded article, comprising the steps of: heating a molded article (A)in no contact with a hot plate so that a surface of the molded article(A) is melted, the molded article (A) comprising a methacrylic resincomprising 80 to 99.9% by mass of a methacrylic acid ester monomer unitand 0.1 to 20% by mass of a unit of at least one additional vinylmonomer copolymerizable with the methacrylic acid ester monomer, whereinthe molded article (A) has a melt flow rate (MFR) of 2.5 g/10 min orlower at 230° C. at a load of 3.8 kg; and welding the molded article (A)with an additional molded article (B).
 18. The method for producing themolded article according to claim 17, wherein the methacrylic resin is amethacrylic resin which has a weight-average molecular weight of 300000or lower as measured by gel permeation chromatography (GPC), and whichcontains 6 to 50% of a component having a molecular weight that is 5times or more lower than a peak top molecular weight (Mp) obtained froma GPC elution curve.
 19. The method for producing the molded articleaccording to claim 17, wherein the methacrylic resin is a methacrylicresin in which an abundance of a component having a molecular weight of250000 or higher obtained from a GPC elution curve is 12% or more of aGPC area.
 20. The method for producing the molded article according toclaim 17, wherein the methacrylic resin has an extrapolated onsettemperature (° C.) of 120° C. or lower as determined from a glasstransition curve obtained by heating from 40° C. to 210° C. at a heatingrate of 10° C./min according to JIS-K-7121 with α-alumina as a referencein a nitrogen gas atmosphere using a differential scanning calorimeter(DSC).
 21. The method for producing the molded article according toclaim 17, wherein the molded article (A) has a water absorption rate of0.5% by mass or lower.
 22. The method for producing the molded articleaccording to claim 17, wherein the molded article (B) is a moldedarticle of an ABS-based resin.